diff --git a/api/swagger.yaml b/api/swagger.yaml
index 366853526f..05a42d307e 100644
--- a/api/swagger.yaml
+++ b/api/swagger.yaml
@@ -231,6 +231,7 @@ definitions:
         type: "string"
       Source:
         description: "Mount source (e.g. a volume name, a host path)."
+        type: "string"
       Type:
         description: |
           The mount type. Available types: